1. Field of the Invention
The invention pertains to a power unit for a passenger vehicle and, more particularly, to a power unit for a passenger vehicle that includes, longitudinally from front to rear, a thermal engine and a transmission, of a kind in which the rear side of a longitudinal block of the thermal engine is rigidly connected to the front side of the transmission housing, especially a housing for an engine flywheel, the housing being of the kind which includes, to the right of the oil pan installation plane beneath the engine block, two horizontal right angle members, facing one another transversely, each one including a longitudinal forward arm secured rigidly to the engine block, and a second rear transverse mounted arm secured rigidly to the transmission housing to strengthen the assembly connection of the power unit and transmission.
2. Discussion of the Background the Invention
Many examples of power plants are known. The object of concern here, for the most part, is with power plant units in which the thermal engine is a powerful engine and in which the output shaft, made as one piece with the crankshaft, is capable of driving the transmission with considerable torque. During operation, due to the vibrations to which the engine is subjected and, more generally, the power plant in its entirety, the attachment points of the engine block to the transmission crank case are subjected to longitudinal bending stresses.
Elsewhere it has also been found that due to the friction that exists between the different bearings of the crankshaft and the output shaft, one part of the engine torque is capable of being partially transmitted, especially during restarts of the engine, to the thermal engine, unit in the form of a torque about the direction of the output shaft of the engine, which has the effect of producing shear stresses on the attachment points of the engine block to the transmission housing, and of causing torsional stresses for the transmission housing.
The attachment points of the engine block to the transmission housing are traditionally made in the form of screw-and-nut connections.
Due to the effect of bending stresses and stresses due to the engine torque that are partially transmitted to the block, these screws and nuts can become deformed, which can have the consequence of causing difficulties when, for example, one wishes to remove the vehicle engine by separating it from the transmission.
The deformation of these bearings can cause accelerated wear of the turning components that they carry as well as leakage of the lubricant.
In order to overcome this disadvantage, it has been suggested that one insert right angle members of the kind described previously between the engine block and one housing of the transmission crank case. This design allows one to strengthen in a satisfactory manner the connection between the engine block and the transmission crankcase, but it also presents many disadvantages.
In order to provide satisfactory attachment, the right angle members must have numerous anchoring points, which make it difficult to install and remove them, from the standpoint of the time one must spend on this operation and the positioning of the anchoring points before the installation.
In other respects, the large number of anchoring points will increase to the same extent the number of machine finishing steps that must be accomplished on the engine block and on the transmission crankcase housing, which increases the manufacturing costs of such an engine block and of the transmission crank case.
Finally, in order to offer sufficient resistance, these right angle members must be made of a material such as cast iron, which will make the power plant unit heavier.
In order to overcome these disadvantages, the present invention recommends right angle members that are integrated with one additional element of the engine block.
For this purpose, the inventions proposes a power plant of the kind described previously, characterized in that it includes a separation piece which is inserted vertically between the engine block and the oil pan, and on which the first arms are secured rigidly forward of the two right angle members.
This separation piece allows one advantageously to benefit from an increase of in the engine lubricating oil capacity and, depending upon the shape of the separation piece, to install different kinds of oil pan on the same engine block.
According to other characteristics of the invention:
(1) The oil pan separation piece has approximately the shape of a parallelepiped whose upper side is complementary to the shape of the periphery of the lower side of the engine block, and whose lower side is complementary to the shape of the periphery of the upper side of the oil pan, in order to allow the adjustment of an oil pan combined with the engine block.
(2) Each right angle member has the shape of a tetrahedron in which the base forms the second rear arm of the right angle, and in which the body forms the first arm of the right angle.
(3) Each tetrahedral right angle member includes, at the vertices of its base, which are most distant from the median axis of the engine, two longitudinal borings for attachment by screwing of the right angle on a complementary perforated surface of the transmission housing.
(4) The body of each right angle member includes a recess, which opens at its base in order to lighten and strengthen the right angle member.
(5) The right angle members are made of the same material as the separation piece.
(6) The separation pieced is obtained by molding, specifically of an aluminum alloy.
(7) The parallelepiped separation piece includes openings that open between its upper and lower sides to allow the passage of moving contact elements of the engine.